1. Field of the Invention
This invention relates to embedded thin film sensors and methods of embedding thin film sensors.
2. Related Art
Embedding sensors into a mass of material allows the sensors to sense the value of a parameter of the mass in a way that often is not possible with surface mounted sensors. Some material data, such as that relating to the internal thermal and mechanical properties of the material, can only be collected by in situ sensors. For example, internal temperature and strain data is obtained by embedding sensors into a component, with information from remote areas being extrapolated from an array of such sensors.
Moreover, due to the shape, size and/or use of the sensor and/or the device being sensed, mounting the sensors to the outside of the mass of the material might not always be possible. Such material masses include tools, dies, and the like, such as molds, drill bits, and cutter bits, elements of machines, such as turbine blades of aero-engines, static components of machines and systems, such as pressure vessels and pipes, and the like.
U.S. Published Patent Application 2004/0184700 to Li et al., incorporated herein by reference in its entirety, discloses a number of embedded sensor structures. In FIGS. 3-4B, the incorporated '700 published patent application illustrates a number of embodiments of an embedded sensor. In FIGS. 4A and 4B, the incorporated '700 published patent application illustrates a method for forming a thin film microelectronic sensor on a metal substrate and putting an encapsulating metal layer over the thin film sensor.
The incorporated '700 published patent application discloses a method for embedding a thin-film sensor in a high temperature metal bulk material. This method calls for a thin-film sensor to be fabricated on the surface of a metal substrate. First, an insulating or dielectric layer is deposited on the surface of the metal substrate. Then, a thin film sensor is fabricated on this surface using standard photolithographic processes. The sensor is then coated with an insulating ceramic layer, coated with a thin seed layer of the metal matrix material, and electroplated with the same bulk metal matrix material to further encapsulate the sensor. The sensor can then be surrounded by the bulk material by casting or by using any other appropriate, known or later-developed process, such that the sensor is placed at the appropriate location within the fabricated component. The incorporated '700 published patent application also describes a number of methods for embedding fiber optic sensors in a high melting temperature bulk material and for collecting data from an embedded sensor.
U.S. Published Patent Application 2007/0092995 to Datta et al., incorporated herein by reference in its entirety, discloses a method for embedding a device in a metal substrate. The method outlined in the incorporated '995 published patent application uses a sacrificial wafer to manufacture the device. The device is first provided on a sacrificial wafer before a high-grade metal substrate is provided over the device and the sacrificial substrate is removed.